1. Field of the Invention
The present invention relates to the bi-directional transmission of data to and from a multiplicity of remote locations to and from a central data processing location. More particularly, the present invention relates to a remote terminal for monitoring and controlling special services especially for subscribers of cable television, hereinafter "CATV," in such applications as pay TV, security, energy consumption, subscriber response and utility reading systems capable of being regularly polled by a centrally located computer controller for status verification and control, utilizing a single CATV channel.
2. Description of the Prior Art
Known examples of related art includes U.S. patents to:
______________________________________ Patentee Serial No. Grant Date Assignee ______________________________________ Thompson et al 3,733,430 May 15, 1973 R.C.A. Hardy et al 3,761,914 Sept. 25, 1973 Bell Television, Inc. Osborn 3,803,491 April 9, 1974 TOCOM, Inc. Kirk et al 3,833,757 Sept. 3, 1974 Computer Television, Inc. Jannery et al 3,859,596 Jan. 7, 1975 Computer Cable, Corp. Takeuchi 3,886,538 May 27, 1975 Hochiki, Corp. Barnhart 3,934,079 Jan. 20, 1976 Jerrold Electronics, Corp. Shomo 3,943,447 Mar. 9, 1976 Comsonics, Inc. Savit 3,990,036 Nov. 2, 1976 Western Geo- physical, Corp. Ricketts et al 3,997,718 Dec. 14, 1976 Magnavox Company Holz 4,031,543 June 21, 1977 Berkeley Vari- tronics Systems Morehead 4,057,829 Nov. 8, 1977 Spectra Dyne Hurney et al 4,074,310 Feb. 14, 1978 Artel Mfg., Corp. ______________________________________
Further examples of related art includes those appearing in trade literature and articles, as follows:
Automatic Meter Reading By Cable by Frank Eldridge, dated August, 1972 herein called "Eldridge." PA0 STRINGING THE WIRED CITY by Gerald Walker, Electronics Magazine, Sept. 27, 1971, herein called "Walker." PA0 The Use of Cable Systems to Solve Traffic Control Communications by Carl Schoeneberger, 1977, herein called "Schoeneberger." PA0 COST BARRIER CRACKED IN TWOWAY CABLE TV by D. Stephens McVoy, Electronics, Feb. 20, 1975, herein called "McVoy." PA0 The Computer In the Living Room by Hubert J. Schlafly, 1973, herein called "Schlafly," released by Telepromter, Corp. PA0 Subscriber Response System by R. T. Callais et al., about 1972, released by Hughes Aircraft Company, herein called "SRS." PA0 ADDRESSABLE TAPS BECOME OF AGE by Joe Hale, T.V. Communications, April, 1976, herein called "DVC Taps." PA0 COMMUNICATIONS CHIP AIDS HOME SECURITY by J. E. Pascente, Electronics, Sept. 15, 1977, herein called "Pascente." PA0 New From Magnavox, data sheet of Magnavox, about 1976, herein called "Magnavox Smart Tap." PA0 Contempo 2001, brochure of Status Systems International, about 1976.
A pertinent example of using bi-directional data transmission through the medium of a single CATV channel for monitoring and controlling multiple remote devices such as subscriber polling, alarms, meter reading, TV channel selection, education and health services and the like is exemplified by the above-described Subscriber Response System (SRS).
The SRS provides each subscriber with a terminal modem coupled with a predetermined CATV channel and includes a local processing center similarly coupled with the CATV channel for periodically and sequentially polling each TM. Each terminal modem houses sufficient interfacing hardware and terminal blocks and jacks so as to convert the particular analog/digital data for up to 30 e.g., input/output data points into a message, together with sufficient data transmission hardware for propagating the message through the selected CATV channel to the central processing unit (CPU).
Each subscriber is interrogated in turn by the CPU until a group (e.g., 1,000) of subscribers has been processed. Following the interrogation period, the CPU then services the subscriber requests. When the subscriber group (e.g. 1,000) has been interrogated and serviced, the process is repeated for the next subscriber group and so on.
The above-described SRS system is deficient in several respects. The modem and data message therefor is fixed at the time of manufacture. This means that the modem only approximates the needs of a typical user and therefore in a large number of cases is either unduly complex or inherently limiting in that it either contains less or more than a particular subscriber needs.
Yet another difficulty with the SRS system is that the data message length is fixed for every subscriber thereby inhibiting subsequent expansion for individual cases and eliminating the capability of adding functions which, at the time of installation, had not yet been envisioned. It is noted that the propagation of unnecessary data for a particular subscriber, when multiplied by a large number of subscribers, results in inefficient and wasteful use of the data transmission medium and limits the frequency at which a particular subscriber can be repeatedly serviced.
The system envisioned by Osborn and made by TOCOM, Inc. also uses terminal modems having internal interfacing and data message lengths which are fixed at the time of manufacturing and thereby is deficient in many of the aforementioned ways. The data transmission sheme described by Osborn uses three simultaneous radio frequency carriers in order to achieve reliable data transmission and low cost home receivers. To further enhance polling rates without thereby necessitating higher data rates, Osborn interrogates a number of units (e.g. 10) on a common frequency, each of which responds to one of ten different frequencies. It is noted that this particular data transmission scheme uses unnecessary band width, entails inordinately complex data controls and, by reducing data transmission rates, results in little or no gain in polling frequencies.
It should be noted that, as evidenced by the above-described patents, articles, and trade literature, a variety of data transmission schemes, addressable data taps and related devices have heretofore been advanced, all of which suffer from the deficiency of being fixed at the time of manufacture to a particular scheme and thereby inherently limit the flexibility of the resultant data transmission system.